The present invention relates to a composition for gas sorption, as well as to devices formed with the composition; the invention also refers to processes for obtaining the composition.
In particular, the invention refers to compositions and devices for sorption of traces of gases, both residual gases in evacuated chambers and impurities in inert gases, in applications in which the space available for the sorbing device is reduced.
Examples of systems requiring the control of the internal atmosphere, but having only limited room for the gas sorbing device, are flat panel displays, both field emission displays (also known as FEDs, generally requiring an inner vacuum atmosphere) and plasma displays (also known as PDPs, inside which there is an atmosphere of a given composition). Another particularly important application is represented by the OLED (Organic Light Emitting Display) screens, in which sorption of moisture from the screen inner space is essential, but it can be necessary also to sorb other gases, such as oxygen or carbon dioxide. Due to the relevance of this application, in the following description reference will be made to these screens, but it is intended that compositions and sorbing devices of the invention can be used in a wide range applications needing gas sorption, particularly when the thickness available for housing the sorbing device is small.
OLED screens are used as displays for mobile phones, for Hi-Fi equipment, for car dashboards and the like. These kinds of screens and the problems related to water entering inside them are disclosed, for example, in U.S. Pat. No. 5,882,761.
The search publication RD 430061 and International Patent Application Publication WO-A-02/27812 of SAES Getters S.p.A. disclose moisture-sorbing systems which are specific for OLEDs. These systems are formed of a part with a central cavity filled with drying material, and welded at the edges to a water-permeable membrane.
U.S. Pat. Nos. 4,985,296 and 5,078,909 and International Patent Application Publication WO-A-01/88041 disclose sorbing systems based on an alternative approach to the problem, namely powders of the material active in gas sorption are incorporated in a resin or in a polymeric material, having gas permeability sufficient to allow gases to reach the particles of sorbing material.
A problem common to all the known sorbing systems is nevertheless that these, once manufactured, must be kept under inert atmosphere, throughout storage time and during transportation, to avoid in these steps any contact with reactive gases and hence their loss of functionality.